Stent and catheter assembly and method for treating bifurcations

ABSTRACT

An apparatus and method is provided for stenting bifurcated vessels. A proximal angled stent is configured for implanting in a side-branch vessel wherein the proximal angled stent has an angulated portion that corresponds to the angle formed by the intersection of the side-branch vessel and the main vessel so that all portions of the side-branch vessel at the bifurcation are covered by the proximal angled stent. A main-vessel stent is provided for implanting in the main vessel, wherein the main-vessel stent has an aperture or stent cell that aligns with the opening to the side-branch vessel to permit unobstructed blood flow between the main vessel and the side-branch vessel. Side-branch and main-vessel catheter assemblies are advanced over a pair of guide wires for delivering, appropriately orienting, and implanting the proximal angled stent and the apertured stent. In one embodiment, a stent delivery assembly is provided for implanting a Y-shaped stent in a bifurcated vessel. A dual balloon Y-shaped catheter is provided having two expandable members. The catheter is delivered over a guide wire while a restraining member holds the expandable members together for low profile delivery.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to stent deployment assemblies for use at abifurcation and, more particularly, a catheter assembly for implantingone or more stents for repairing bifurcations, the aorto-ostium, andbifurcated blood vessels that are diseased, and a method and apparatusfor delivery and implantation.

[0003] 2. Prior Art

[0004] Stents conventionally repair blood vessels that are diseased andare generally hollow and cylindrical in shape and have terminal endsthat are generally perpendicular to its longitudinal axis. In use, theconventional stent is positioned at the diseased area of a vessel and,after placement, the stent provides an unobstructed pathway for bloodflow.

[0005] Repair of vessels that are diseased at a bifurcation isparticularly challenging since the stent must overlay the entirediseased area at the bifurcation, yet not itself compromise blood flow.Therefore, the stent must, without compromising blood flow, overlay theentire circumference of the ostium to a diseased portion and extend to apoint within and beyond the diseased portion. Where the stent does notoverlay the entire circumference of the ostium to the diseased portion,the stent fails to completely repair the bifurcated vessel. Where thestent overlays the entire circumference of the ostium to the diseasedportion, yet extends into the junction comprising the bifurcation, thediseased area is repaired, but blood flow may be compromised in otherportions of the biflurcation. Unopposed stent elements may promote lumencompromise during neointimalization and healing, producing restenosisand requiring further procedures. Moreover, by extending into thejunction comprising the bifurcation, the stent may block access toportions of the bifurcated vessel that require performance of furtherinterventional procedures. Similar problems are encountered when vesselsare diseased at their angled origin from the aorta as in the ostium of aright coronary or a vein graft. In this circumstance, a stent overlyingthe entire circumference of the ostium extends back into the aorta,creating problems, including those for repeat catheter access to thevessel involved in further interventional procedures.

[0006] Conventional stents are designed to repair areas of blood vesselsthat are removed from bifurcations and, since a conventional stentgenerally terminates at right angles to its longitudinal axis, the useof conventional stents in the region of a vessel bifurcation may resultin blocking blood flow of a side branch or fail to repair thebifurcation to the fullest extent necessary. The conventional stentmight be placed so that a portion of the stent extends into the pathwayof blood flow to a side branch of the bifurcation or extend so far as tocompletely cover the path of blood flow in a side branch. Theconventional stent might alternatively be placed proximal to, but notentirely overlaying the circumference of the ostium to the diseasedportion. Such a position of the conventional stent results in abifurcation that is not completely repaired. The only conceivablesituation that the conventional stent, having right-angled terminalends, could be placed where the entire circumference of the ostium isrepaired without compromising blood flow, is where the bifurcation isformed of right angles. In such scenarios, extremely precise positioningof the conventional stent is required. This extremely precisepositioning of the conventional stent may result with the right-angledterminal ends of the conventional stent overlying the entirecircumference of the ostium to the diseased portion without extendinginto a side branch, thereby completely repairing the right-angledbifurcation.

[0007] To circumvent or overcome the problems and limitations associatedwith conventional stents in the context of repairing diseased bifurcatedvessels, a stent that consistently overlays the entire circumference ofthe ostium to a diseased portion, yet does not extend into the junctioncomprising the bifurcation, may be employed. Such a stent would have theadvantage of completely repairing the vessel at the bifurcation withoutobstructing blood flow in other portions of the bifurcation. Inaddition, such a stent would allow access to all portions of thebifurcated vessel should further interventional treatment be necessary.In a situation involving disease in the origin of an angulatedaorto-ostial vessel, such a stent would have the advantage of completelyrepairing the vessel origin without protruding into the aorta orcomplicating repeat access.

[0008] In addition to the problems encountered by using the prior artstents to treat bifurcations, the delivery platform for implanting suchstents has presented numerous problems. For example, a conventionalstent is implanted in the main vessel so that a portion of the stent isacross the side branch, so that stenting of the side branch must occurthrough the main-vessel stent struts. In this method, commonly referredto in the art as the “monoclonal antibody” approach, the main-vesselstent struts must be spread apart to form an opening to the side-branchvessel and then a catheter with a stent is delivered through theopening. The cell to be spread apart must be randomly and blindlyselected by recrossing the deployed stent with a wire. The drawback withthis approach is there is no way to determine or guarantee that themain-vessel stent struts are properly oriented with respect to the sidebranch or that the appropriate cell has been selected by the wire fordilatation. The aperture created often does not provide a clear openingand creates a major distortion in the surrounding stent struts. Thedrawback with this approach is that there is no way to tell if themain-vessel stent struts have been properly oriented and spread apart toprovide a clear opening for stenting the side-branch vessel.

[0009] In another prior art method for treating bifurcated vessels,commonly referred to as the “Culotte technique,” the side-branch vesselis first stented so that the stent protrudes into the main vessel. Adilatation is then performed in the main vessel to open and stretch thestent struts extending across the lumen from the side-branch vessel.Thereafter, the main-vessel stent is implanted so that its proximal endoverlaps with the side-branch vessel. One of the drawbacks of thisapproach is that the orientation of the stent elements protruding fromthe side-branch vessel into the main vessel is completely random.Furthermore the deployed stent must be recrossed with a wire blindly andarbitrarily selecting a particular stent cell. When dilating the mainvessel stretching the stent struts is therefore random, leaving thepossibility of restricted access, incomplete lumen dilatation, and majorstent distortion.

[0010] In another prior art device and method of implanting stents, a“T” stent procedure includes implanting a stent in the side-branchostium of the bifurcation followed by stenting the main vessel acrossthe side-branch ostium. In another prior art procedure, known as“kissing” stents, a stent is implanted in the main vessel with aside-branch stent partially extending into the main vessel creating adouble-barreled lumen of the two stents in the main vessel distal to thebifurcation. Another prior art approach includes a so-called “trouserlegs and seat” approach, which includes implanting three stents, onestent in the side-branch vessel, a second stent in a distal portion ofthe main vessel, and a third stent, or a proximal stent, in the mainvessel just proximal to the bifurcation.

[0011] All of the foregoing stent deployment assemblies suffer from thesame problems and limitations. Typically, there is uncovered intimalsurface segments on the main vessel and side-branch vessels between thestented segments. An uncovered flap or fold in the intima or plaque willinvite a “snowplow” effect, representing a substantial risk for subacutethrombosis, and the increased risk of the development of restenosis.Further, where portions of the stent are left unopposed within thelumen, the risk for subacute thrombosis or the development of restenosisagain is increased. The prior art stents and delivery assemblies fortreating bifurcations are difficult to use, making successful placementnearly impossible. Further, even where placement has been successful,the side-branch vessel can be “jailed” or covered so that there isimpaired access to the stented area for subsequent intervention. Thepresent invention solves these and other problems as will be shown.

[0012] In addition to problems encountered in treating disease involvingbifurcations for vessel origins, difficulty is also encountered intreating disease confined to a vessel segment but extending very closeto a distal branch point or bifurcation which is not diseased and doesnot require treatment. In such circumstances, very precise placement ofa stent covering the distal segment, but not extending into the ostiumof the distal side-branch, may be difficult or impossible. The presentinvention also offers a solution to this problem.

[0013] References to distal and proximal herein shall mean: the proximaldirection is moving away from or out of the patient and distal is movingtoward or into the patient. These definitions will apply with referenceto body lumens and apparatus, such as catheters, guide wires, andstents.

SUMMARY OF THE INVENTION

[0014] The invention provides for improved stent designs and stentdelivery assemblies for repairing a main vessel and side-branch vesselforming a bifurcation, without compromising blood flow in other portionsof the bifurcation, thereby allowing access to all portions of thebifurcated vessels should further interventional treatment be necessary.In addition, it provides an improved stent design and stent deliverysystem for repairing disease confined to the aorto-ostium of a vesselwithout protrusion into the aorta. The stent delivery assemblies of theinvention all share the novel feature of containing, in addition to atracking guide wire, a second positioning wire which affects rotationand precise positioning of the assembly for deployment of the stent.

[0015] The present invention includes a proximal angled stent forimplanting in a side-branch vessel adjacent to a bifurcation. Thecylindrical member can have substantially any outer wall surface typicalof conventional stents used, for example, in the coronary arteries. Thecylindrical member of the proximal angled stent has a distal end forminga first plane section that is substantially transverse to thelongitudinal axis of the stent. The proximal end of the stent forms asecond plane section that is at an angle, preferably an acute angle,relative to the longitudinal axis of the stent. The acute angle isselected to approximately coincide with the angle formed by theintersection of the side-branch vessel and the main vessel so that noportion of the stented area in the side-branch vessel is left uncovered,and no portion of the proximal angled stent extends into the mainvessel.

[0016] A second stent is provided for implanting in the main vesseladjacent to a bifurcation in which a cylindrical member has distal andproximal ends and an outer wall surface therebetween, which cantypically be similar to the outer wall surface of stents used in thecoronary arteries. An aperture is formed in the outer wall surface ofthe apertured stent and is sized and positioned on the outer wallsurface so that when the apertured stent is implanted in the mainvessel, the aperture is aligned with the side-branch vessel and theproximal angled stent in the side-branch vessel, providing unrestrictedblood flow from the main vessel through to the side-branch vessel.Deployment of the angled and apertured stents is accomplished by a novelstent delivery system adapted specifically for treating bifurcatedvessels.

[0017] In one embodiment for implanting the proximal angled stent, aside-branch catheter is provided in which a tracking guide wire lumenextends within at least a portion of the side-branch catheter, beingdesigned to be either an over-the-wire or rapid exchange-type catheter.An expandable member is disposed at the distal end of the side-branchcatheter. A tracking guide wire is provided for slidable movement withinthe tracking guide wire lumen. A positioning guide wire lumen isassociated with the catheter and the expandable member, such that aportion of the positioning guide wire lumen is on the outer surface ofthe catheter and it approaches the proximal end of the outer surface ofthe expandable member. A stent-positioning guide wire is provided forslidable movement within the positioning lumen. The proximal ends of thetracking and stent-positioning guide wires extend out of the patient andcan be simultaneously manipulated so that the distal end of thestent-positioning guide wire is advanced in the main vessel distal to aside-branch vessel, and the distal end of the tracking guide wire isadvanced into the side-branch vessel distal to the target area. In oneembodiment, the stent-positioning guide wire lumen includes an angulatedsection so that the stent-positioning guide wire advanced in the mainvessel distal to the side-branch vessel results in rotation causing theproximal angled stent to assume the correct position in the side-branchvessel. The positioning lumen functions to orient the stent-positioningguide wire to rotate or torque the side-branch catheter to properlyalign and position the proximal angled stent in the side-branch vessel.

[0018] The side-branch catheter assembly is capable of delivering theproximal angled stent, mounted on the expandable member, in theside-branch vessel. The side-branch catheter could also be configuredfor delivering a self-expanding proximal angled stent.

[0019] The stent delivery system of the present invention furtherincludes a main-vessel catheter for delivering a stent in the mainvessel after the side-branch vessel has been stented. The main-vesselcatheter includes a tracking guide wire lumen extending through at leasta portion thereof, and adapted for receiving a tracking guide wire forslidable movement therein. An expandable member is positioned near themain-vessel catheter distal end for delivering and implanting amain-vessel (apertured) stent in the main vessel. The main-vessel stentincludes an aperture on its outer surface which aligns with theside-branch vessel. A positioning guide wire lumen is associated withthe expandable member, and is sized for slidably receiving thestent-positioning guide wire. The stent-positioning guide wire slideswithin the positioning guide wire lumen to orient the expandable memberso that it is positioned adjacent to, but not in, the side-branch vesselwith the stent aperture facing the side-branch ostium.

[0020] In one embodiment, both the side-branch catheter and main-vesselcatheter assemblies include the so-called rapid exchange catheterfeatures which are easily exchangeable for other catheters while thetracking and positioning guide wires remain positioned in theside-branch vessel and the main vessel, respectively. In an alternateembodiment, both catheters may be of the “over-the-wire” type.

[0021] The present invention further includes a method for deliveringthe proximal angled and the main-vessel (apertured) stents in thebifurcated vessel. In one embodiment of the side-branch catheter system(side-branch catheter plus proximal angled stent), the distal end of thetracking guide wire is advanced into the side-branch vessel and distalto the target area. The side-branch catheter is then advanced along thetracking guide wire until the distal end of the catheter is justproximal of entering the side-branch. The distal end of the integrated,stent-positioning guide wire is then advanced by the physician pushingthe guide wire from outside the body. The distal end of thestent-positioning wire travels through the positioning guide wire lumenand passes close to the proximal end of the proximal angled stent andexpandable member and exits the lumen. The wire is advanced in the mainvessel until the distal end is distal to the side-branch vessel. Thecatheter is then advanced into the side branch until resistance is feltfrom the stent-positioning guide wire pushing up against the ostium ofthe side-branch vessel causing the proximal angled stent to rotate intoposition and arresting its advancement at the ostium. Thereafter, theproximal angled stent, mounted on the expandable member, is alignedacross the target area and the angled proximal end of the stent isaligned at the intersection of the side-branch vessel and the mainvessel (the ostium of the side-branch vessel) so that the stentcompletely covers the target area in the side-branch vessel, yet doesnot extend into the main vessel, thereby blocking blood flow. Theexpandable member is expanded thereby expanding and implanting theproximal angled stent in the side-branch vessel. The positioning wireprevents forward movement of the expandable member and proximal angledstent during inflation. Thereafter, the expandable member is deflatedand the side-branch catheter assembly is withdrawn from the patient in aknown rapid-exchange manner. In this embodiment, the side-branchcatheter is designed so that both the side-branch tracking guide wireand main-vessel positioning guide wire can be left in their respectivevessels should sequential or simultaneous high pressure ballooninflation be required in each of the vessels in order to complete thestenting procedure. In other words, the integrated positioning wire canbe unzipped from the proximal 100 cm of the catheter thereby allowing itto act as a rapid exchange wire. Preferably, high pressure balloons areinflated simultaneously in the main vessel and proximal angled stents inorder to avoid deforming one stent by unopposed balloon inflation withinthe other one. This additional step of high pressure balloon inflationis a matter of physician choice. A further advantage of this embodimentis that by waiting to advance the integrated stent-positioning wire outof catheter only when the catheter distal end is near the target area,wire wrapping, encountered in an embodiment utilizing two non-integratedguide wires, is avoided. Utilizing this method, the side-branch vesselcan be stented without the need for stenting the main vessel.

[0022] In an aorto-ostial application of the side-branch catheterassembly (side-branch catheter plus proximal angulated stent), thepositioning wire is advanced into the aortic root while the trackingwire is advanced into the right coronary or vein graft whose angulatedorigin is to be stented. After advancement of the proximal-angled stent,mounted on the expanding member, it is aligned across the target areaand the angled proximal end of the stent is aligned at the ostium.

[0023] In the event that the main vessel is to be stented (with thestent placed across the bifurcation site), the proximal end of themain-vessel guide wire is inserted into the distal end of the guide wirelumen of the main-vessel catheter. The side-branch wire would be removedfrom the side branch at this time. The main-vessel catheter would thenbe advanced into the body until the catheter is within one cm or so ofthe target site. The distal end of the second (integrated,stent-positioning) guide wire, which resides in the main-vessel catheterduring delivery to the main vessel, is then advanced by having thephysician push the positioning wire from outside the body. The distalend of the stent-positioning wire travels through the positioning guidewire lumen and passes underneath the proximal half of the stent until itexits at the site of the stent aperture or a designated stent cell wherean aperture can be formed. The catheter is then advanced distally untilresistance is felt from the stent-positioning guide wire pushing upagainst the ostium of the side-branch vessel indicating that the stentaperture is correctly facing the side-branch vessel ostium and isaligned with the proximal end of the proximal angled stent. Thereafter,the expandable member on the main-vessel catheter is inflated, therebyexpanding and implanting the main-vessel stent into contact with themain vessel, with the aperture in the stent providing a flow path forthe blood from the main vessel through to the side-branch vessel withoutany obstructions. The expandable member is deflated and the main-vesselcatheter is removed from the body. The main-vessel catheter is designedso that both the main-vessel guide wire and side-branch wire can be leftin their respective vessels should sequential or simultaneous highpressure balloon inflation be required in each of the vessels in orderto complete the stenting procedure. The presence of thestent-positioning wire in the stent aperture permits catheter accessthrough this aperture into the side-branch vessel for balloon inflationto smooth out the aperture in the main-vessel stent. This additionalstep is a matter of physician choice.

[0024] Utilizing this method, the main vessel can be stented without theneed for stenting the side-branch vessel. An advantage of thisembodiment is that a major side branch, not diseased and requiringtreatment, exiting from a main vessel requiring stenting, may beprotected by the positioning wire while the main vessel is stented. If“snowplowing” compromise or closure of the side-branch vessel occurswith main-vessel stenting, then access is already present and guaranteedfor stenting of the side-branch vessel over the wire already in place inthe manner described above. This will allow confident stenting of a mainvessel segment containing a major side branch. In this usage, only ifcompromise or occlusion of the side branch occurs, will additionalstenting of the side branch be required.

[0025] In an alternative embodiment, a main-vessel stent that does nothave an aperture on its outer surface is mounted on the main-vesselcatheter and is implanted in the main vessel so that it spans theopening to the side-branch vessel. Thereafter, a balloon catheter isinserted through a targeted (non-random) stent cell of the main-vesselstent, which is centered precisely facing the side-branch ostium, sothat the balloon partially extends into the side-branch vessel. Thisballoon has tracked over the positioning wire which has been left inplace through the targeted stent cell during and after deployment of themain vessel stent. The balloon is expanded, forming an opening throughthe stent struts that corresponds to the opening of the side-branchvessel, providing a blood-flow path through the main vessel andmain-vessel stent and into the side-branch vessel. A proximal angledstent mounted on a side-branch catheter is then advanced through themain-vessel stent and the opening formed in the targeted stent cellthrough to the side-branch vessel. The proximal angled stent is expandedand implanted in the side-branch vessel so that all portions of theside-branch vessel are covered by the stent in the area of thebifurcation. After the main-vessel stent and the side-branch vesselproximal angled stent are implanted, an uncompromised blood-flow path isformed from the main vessel through the main-vessel stent and openinginto the side-branch vessel, and through the side-branch vessel proximalangled stent.

[0026] In another alternative embodiment, a stent having a distal angleis implanted in the main vessel. In portions of the main vessel havingdisease that approaches and is directly adjacent to the side-branchvessel, a distal angle stent is implanted using the novel catheter ofthe present invention so that the stent covers the diseased area, butdoes not jail or cover the opening to the side-branch vessel.

[0027] In another alternative embodiment, a Y-shaped catheter andY-shaped stent are provided for stenting a bifurcated vessel. In thisembodiment, a dual balloon catheter has a Y-shaped stent mounted on theballoons and the balloons are positioned side by side for easierdelivery. The balloons are normally biased apart, but are restrained andheld together to provide a low profile during delivery of the stent. Aguide wire is first positioned in a main vessel at a point distal to thebifurcation. A second guide wire is retained in the catheter in a secondguide wire lumen while the catheter is advanced over the tracking guidewire so that the balloons and stent are distal to the bifurcation. Thetracking guide wire is then withdrawn proximally thereby releasing theballoons which spring apart. The catheter is withdrawn proximally untilit is proximal to the bifurcation. As the catheter is withdrawnproximally, one of the two guide wires is left in the main vessel. Theother guide wire is then advanced into the side-branch vessel. Thecatheter is then advanced over both guide wires until the balloons andstent are anchored in the bifurcation. The balloons are inflated and thestent expanded and implanted in the bifurcation.

[0028] In another aspect of the invention, there is provided anapparatus and method for stenting a bifurcated vessel having abifurcation, a first vessel branch, and a second vessel branch. A dualballoon Y-shaped catheter is provided and includes a first expandablemember and a second expandable member. A first lumen is provided forreceiving a restraining member. The first lumen extends through at leasta portion of the catheter including the first expandable member. Asecond lumen is provided for receiving a guide wire. The second lumenextends through at least a portion of the catheter including the secondexpandable member. A Y-shaped stent is mounted on the first and secondexpandable members. A restraining member is positioned within the firstlumen such that the first expandable member and the second expandablemember are normally biased apart, but are restrained and held togetherby the restraining member. A guide wire is then positioned distally ofthe bifurcation in the first vessel branch. The guide wire is loadedinto the second lumen. The catheter is advanced over the guide wire sothat the catheter is advanced proximate the bifurcation. The restrainingmember can then be retracted proximally until the first expandablemember and the second expandable member are released and spring apart. Awire is then advanced distally through the first lumen into the secondvessel branch. The catheter is advanced distally over the wire and guidewire until the Y-shaped stent is positioned at the bifurcation. TheY-shaped stent can then be implanted by inflating the first and secondexpandable members. The first and second expandable members are thendeflated. The catheter, wire, and guide wire are then withdrawn.

[0029] In another embodiment two apertured stents are implanted to coverthe bifurcated vessels. A main-vessel stent has a cylindrical shapehaving a heavy cell density on the distal half and light cell density onthe proximal half, and an aperture on its outer surface at the junctionat these two halves. A main-vessel stent is first implanted in the mainvessel so that its aperture aligns with the ostium of the side-branchvessel, thereby covering the main vessel proximally with light celldensity and distally with heavy cell density. A second main-vessel stentis then implanted over a tracking wire into the side branch so that theheavy cell density portion of the stent is implanted in the side-branchvessel, the light cell density is implanted in the main vessel andoverlaps the light cell density of the proximal end of the main-vesselstent, and the aperture faces the main vessel as it departs from theside branch. Combined densities of proximal light cell portions proximalto the bifurcation are similar to the heavy cell densities in each limbdistal to the bifurcation. Respective apertures of each of the twomain-vessel stents are aligned with the respective ostia of both limbsof the bifurcation (main vessel and side branch).

[0030] Other features and advantages of the present invention willbecome apparent from the following detailed description, taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 is an elevational view of a bifurcation in which a priorart “T” stent is in a side-branch ostium followed by the stenting of themain vessel across the branch ostium.

[0032]FIG. 2 is an elevational view of a bifurcation in which “touching”prior art stents are depicted in which one stent is implanted in theside branch, a second stent implanted in a proximal portion of the mainvessel next to the branch stent, with interrupted placement of a thirdstent implanted more distally in the main vessel.

[0033]FIG. 3 is an elevational view of a bifurcation depicting “kissing”stents where a portion of one stent is implanted in both the side-branchand the main vessel and adjacent to a second stent implanted in the mainvessel creating a double-barreled lumen in the main vessel distal to thebifurcation.

[0034]FIG. 4 is an elevational view of a prior art “trouser legs andseat” stenting approach depicting one stent implanted in the side-branchvessel, a second stent implanted in a proximal portion of the mainvessel, and a close deployment of a third stent distal to thebifurcation leaving a small gap between the three stents of an uncoveredluminal area.

[0035]FIG. 5A is a perspective view of a stent of the present inventionhaving an angled proximal end.

[0036]FIG. 5B is a side elevational view of the proximal angled stent ofFIG. 5A depicting the distal end being transverse to the longitudinalaxis of the stent, and the proximal end at an angle of less than 90°.

[0037]FIG. 5C is an elevational view of a bifurcation in which a priorart stent is implanted in the side-branch vessel.

[0038]FIG. 5D is an elevational view of a bifurcation in which a priorart stent is implanted in the side-branch vessel, with the proximal endof the stent extending into the main vessel.

[0039]FIG. 5E is an elevational view of a bifurcation in which theproximal angled stent of the present invention, as depicted in FIGS. 5Aand 5B, is implanted in the side-branch vessel.

[0040]FIG. 6A is a perspective view depicting the main-vessel stent ofthe present invention in which an aperture is formed on the outersurface of at least a portion of the stent.

[0041]FIG. 6B is a side elevational view of the main-vessel stent ofFIG. 6A.

[0042]FIG. 7A is an elevational view, partially in section, of aside-branch catheter assembly depicting the distal end of the catheterwith the expandable member and the second guide wire lumen attachedthereto, for receiving the integrated stent-positioning guide wire,while the tracking guide wire is received by the main guide wire lumen.

[0043]FIG. 7B is an elevational view, partially in section, of thecatheter assembly of FIG. 7A, in which the stent positioning guide wireis advanced out of the catheter.

[0044]FIG. 8 is an elevational view, partially in section, of aside-branch catheter assembly depicting an expandable balloon having anangled proximal portion corresponding to the angle of the proximalangled stent.

[0045]FIG. 9A is an elevational view of a bifurcated vessel in which aside-branch racking guide wire has been advanced into a side-branchvessel, with the stent-positioning guide wire remaining within thecatheter until the catheter assembly is just proximal to the side-branchvessel.

[0046]FIG. 9B is an elevational view of a bifurcation in which aside-branch tracking guide wire has been advanced through the patient'svascular system into a side branch, and a stent-positioning guide wirehas been advanced through the patient's vascular system and into themain vessel distal to the ostium of the side-branch vessel.

[0047]FIG. 10A is an elevational view of a bifurcation in which theside-branch catheter assembly has been advanced in the patient'svasculature so that the proximal angled stent mounted on the expandablemember is positioned in the target area of the side-branch vessel.

[0048]FIG. 10B is an elevational view of the side-branch catheterassembly of FIG. 10A in which the proximal angled stent has beenexpanded by the balloon portion of the catheter in the side-branchvessel.

[0049] FIGS. 11A-11D are partial elevational views in which theside-branch catheter assembly of FIG. 10A is used to implant theproximal angled stent in the side-branch vessel where the proximalangled stent is rotated to be properly aligned for implanting in thevessel.

[0050] FIGS. 12A-12C depict an elevational view, partially in section,of a main-vessel catheter assembly in which the main vessel stent has anaperture on its outer surface.

[0051] FIGS. 12D-12F depict an elevational view, partially in section,of the main-vessel catheter of FIGS. 12A-12C with a ramp to help orientand advance the guide wire through the aperture in the main-vesselstent.

[0052] FIGS. 12G-12I depict an elevational view, partially in section,of an alternative embodiment of the main-vessel catheter of FIGS.12A-12C in which the guide wire lumen is angled to pass under the stentand exit through the stent aperture.

[0053] FIGS. 12J-12L depict an elevational view, partially in section,of an alternative embodiment of the main-vessel catheter of FIGS.12A-12C in which a portion of the guide wire lumen passes under thestent.

[0054] FIGS. 13A-13E are elevational views, partially in section,depicting the main-vessel catheter assembly of FIG. 12A and themain-vessel stent in which two guide wires are used to correctlyposition the main vessel stent so that the aperture in the stent isaligned with the side-branch vessel.

[0055]FIG. 14 is an elevational view of a bifurcated vessel in which theproximal angled stent is implanted in the side-branch vessel and a mainvessel stent is implanted in the main vessel.

[0056]FIG. 15 is a perspective view of the main-vessel stent of thepresent invention for deployment in the main vessel, where a targetedstent cell provides an opening through which a guide wire can pass.

[0057] FIGS. 16A-16D are elevational views, partially in section, of amain vessel catheter having the main vessel stent of FIG. 15 mountedthereon, and its relationship to the guide wire for advancing through atargeted stent cell.

[0058]FIG. 17 is an elevational view of a bifurcation in which amain-vessel stent is positioned in a main vessel so that it spans theopening to the side-branch vessel.

[0059]FIG. 18 is an elevational view of a bifurcation in which amain-vessel stent is implanted in the main vessel and a balloon catheteris partially inserted into a side-branch vessel to form an openingthrough the targeted stent cell of the main stent.

[0060] FIGS. 19A-19C are elevational views of a bifurcation in which amain-vessel stent is first implanted in the main vessel and a catheterassembly next deploys a proximal angled stent in a side-branch vessel.

[0061]FIGS. 19D and 19E are cross-sectional views looking down theside-branch vessel at an expanded main vessel prior art stent in which arandom, sub-optimal stent cell was entered and expanded.

[0062]FIGS. 19F is a cross-sectional view looking down the side-branchvessel at an expanded main-vessel stent of the invention in which propertargeted stent cell was entered and expanded.

[0063]FIG. 20A is an elevational view, partially in section, depicting amain vessel catheter in which the main vessel stent is mounted over apositioning guide wire lumen.

[0064]FIG. 20B is an elevational view, partially in section, of a mainvessel catheter depicting the main vessel stent mounted over a sectionof the positioning guide wire lumen, with a distal portion of the guidewire lumen associated with the distal tip of the catheter.

[0065]FIG. 20C is an elevational view, partially in section, of thecatheter of FIG. 20B depicting the positioning guide wire advanced outof the positioning guide wire lumen.

[0066]FIG. 20D is an elevational view, partially in section, depicting amain-vessel stent implanted in the main vessel without jailing orcovering the side-branch vessel.

[0067]FIG. 20E is an elevational view, partially in section, depictingthe main-vessel catheter of FIG. 20A having a ramp to assist inpositioning the guide wire.

[0068]FIG. 20F is an elevational view, partially in section, of a distalangled stent being implanted in the main vessel without jailing theside-branch vessel.

[0069]FIGS. 21 and 22 are elevational views, partially in section,depicting an alternative embodiment of the main-vessel catheter of FIG.20B in which the distal end of the guide wire lumen springs away fromthe expandable balloon.

[0070] FIGS. 23A-23B, 24A-24B, 25A-25B, and 26A-26B, are elevationalviews of various bifurcations which are indicated for receiving mainvessel and side-branch vessel stents deployed by the catheters of thepresent invention.

[0071]FIG. 27A is an elevational view, partially in section, depictingan alternative embodiment in which a Y-shaped catheter assembly deploysa Y-shaped stent in the bifurcation.

[0072]FIG. 27B is an elevational view depicting an alternativeembodiment in which a dual balloon catheter assembly deploys a Y-shapedstent in the bifurcation.

[0073]FIG. 28 is an elevational view depicting the Y-shaped catheterassembly of FIG. 27A in which the stent is mounted on the balloonportions of the catheter.

[0074]FIG. 29A is an elevational view, partially in section of abifurcation in which the Y-shaped catheter of FIG. 27A is delivering thestent in the bifurcated area, tracking over the wire that joins the twotips together.

[0075]FIG. 29B is an elevational view, partially in section, of abifurcation in which the delivered Y-shaped balloon components have beenreleased and spread apart by withdrawal of the tracking wire from theother balloon tip lumen.

[0076]FIG. 29C is an elevational view, partially in section, of theY-shaped delivery catheter of FIG. 27A in which the Y-shaped balloon hasbeen withdrawn proximal to the bifurcation, leaving the first wire inthe right branch.

[0077]FIG. 30 is an elevational view, partially in section, of theY-shaped delivery catheter of FIG. 27A in which the second guide wire isadvanced into the left branch.

[0078]FIG. 31 is an elevational view depicting the Y-shaped catheter ofFIG. 27A in which the Y-shaped stent is implanted in the side branch andmain vessels of the bifurcation.

[0079]FIG. 32 is an elevational view, partially in section, depictingthe Y-shaped catheter assembly of FIG. 27A in which the Y-s h aped stenthas been implanted and the balloon portions of the catheter have beendeflated.

[0080]FIG. 33 is an elevational view depicting a bifurcated vessel inwhich the catheter of FIG. 27A has been withdrawn after implanting theY-shaped stent.

[0081]FIG. 34 is an elevational view depicting a modified stent havingan aperture in its sidewall and in which half of the stent has a heavystent cell density while the other half of the stent has a light stentcell density.

[0082]FIG. 35 is an elevational view depicting the stent of FIG. 34combined to form a stent having a heavy stent cell density in allportions.

[0083]FIG. 36A is an elevational view depicting a bifurcation, in whichthe stent of FIG. 35 has been implanted so that the aperture correspondsto the side-branch vessel and the stent is implanted in the main vessel.

[0084]FIG. 36B is an elevational view depicting a bifurcating vessel inwhich the stent of FIG. 34 has been implanted so that the heavy stentcell density is in the side-branch vessel and the light cell density isin the main vessel. The aperture corresponds to the continuing lumen ofthe main vessel.

[0085]FIG. 36C is an elevational view depicting a bifurcated vessel inwhich two stents of FIG. 34 have been implanted in the side-branchvessel and the main vessel respectively so that the light stent celldensity of each overlaps with the light cell density of the otherthereby creating cell density proximal to the bifurcation similar to theheavy cell density present in each limb distal to the bifurcation.

[0086]FIG. 37 is an elevational view, partially in section, depictinganother alternative embodiment in which a Y-shaped catheter assemblydeploys a Y-shaped stent in the bifurcation.

[0087]FIG. 38 is an elevational view depicting the Y-shaped catheterassembly of FIG. 37 in which a Y-shaped stent is mounted on the balloonportions of the catheter.

[0088]FIG. 39 is an elevational view, partially in section, of theY-shaped delivery catheter and Y-shaped stent of FIG. 38 in which theY-shaped balloon has been advanced proximate to the bifurcation.

[0089]FIG. 40 is an elevational view, partially in section, of theY-shaped delivery catheter of FIG. 37 in which a restraining member isadvanced into the left branch.

[0090]FIG. 41 is an elevational view depicting the Y-shaped catheter ofFIG. 37 in which the Y-shaped stent is implanted in the side branch andmain vessels of the bifurcation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0091] The present invention includes an assembly and method fortreating bifurcations in, for example, the coronary arteries, veins,arteries, and other vessels in the body. Prior art attempts atimplanting intravascular stents in a bifurcation have proved less thansatisfactory. For example, FIGS. 1-4 depict prior art devices whichinclude multiple stents being implanted in both the main vessel and aside-branch vessel. In FIG. 1, a prior art “T” stent is implanted suchthat a first stent is implanted in the side branch near the ostium ofthe bifurcation, and a second stent is implanted in the main vessel,across the side-branch ostium. With this approach, portions of theside-branch vessel are left uncovered, and blood flow to the side-branchvessel must necessarily pass through the main-vessel stent, causingpossible obstructions or thrombosis.

[0092] Referring to FIG. 2, three prior art stents are required to stentthe bifurcation. In FIG. 3, the prior art method includes implanting twostents side by side, such that one stent extends into the side-branchvessel and the main vessel, and the second stent is implanted in themain vessel. This results in a double-barreled lumen which can presentproblems such as thrombosis, and turbulence in blood flow. Referring tothe FIG. 4 prior art device, a first stent is implanted in theside-branch vessel, a second stent is implanted in a proximal portion ofthe main vessel, and a third stent is implanted distal to thebifurcation, thereby leaving a small gap between the stents and anuncovered luminal area.

[0093] All of the prior art devices depicted in FIGS. 1-4 have variousdrawbacks which have been solved by the present invention.

[0094] In one embodiment of the present invention, as depicted in FIGS.5A, 5B and 5E, proximal angled stent 10 is configured for deployment inside-branch vessel 5. Proximal angled stent 10 includes a cylindricalmember 11 having longitudinal axis 12 which is an imaginary axisextending through cylindrical member 11. Distal end 13 and proximal end14 define the length of cylindrical member 11. First plane section 15 isdefined by a plane section through distal end 13 of the cylindricalmember, and second plane section 16 is defined by a plane sectionthrough proximal end 14 of the cylindrical member. Second plane section16 defines acute angle 18, which is the angle between second planesection 16 and longitudinal axis 12.

[0095] In treating side-branch vessel 5, if a prior art stent is used inwhich there is no acute angle at one end of the stent to match the angleof the bifurcation, a condition as depicted in FIGS. 5C and 5D willoccur. That is, a stent deployed in side-branch vessel 5 will leave aportion of the side-branch vessel exposed, or as depicted in SD, aportion of the stent will extend into main-vessel 6. As depicted in FIG.5E, proximal angled stent 10 of the present invention has an acute angle18 that approximates the angle formed by the bifurcation 4 ofside-branch vessel 5 and main-vessel 6. Thus, acute angle 18 is intendedto approximate the angle formed by the intersection of side-branch 5 andmain-vessel 6. The angle between side-branch vessel 5 and main-vessel 6will vary for each application, and for purposes of the presentinvention, should be less than 90°. If there is a 90° angle between theside-branch vessel and the main vessel, a conventional stent having endsthat are transverse to the stent longitudinal axis, would be suitablefor stenting the side-branch vessel.

[0096] The proximal angled stent can be implanted in the side-branchvessel to treat a number of angulated ostial lesions including, but notlimited to, the following:

[0097] 1. The ostium of a left anterior descending artery (LAD) wherethere is a circumflex or trifurcation vessel at less than 90° in itsdeparture from the LAD.

[0098] 2. The ostium of the circumflex artery or a trifurcation in asimilar situation as number 1.

[0099] 3. The ostium of a sizeable diagonal.

[0100] 4. The LAD just distal to, but sparing, the origin of a diagonal.

[0101] 5. The ostium of a circumflex marginal artery with an angulatedtake-off.

[0102] 6. Disease in the circumflex artery just distal to a marginaltake-off, but sparing that take-off.

[0103] 7. The aorta-ostium of a right coronary artery with an angledtake-off.

[0104] 8. The origin of an angulated posterior descending artery.

[0105] 9. The origin of an LV extension branch just at and beyond thecrux, sparing the posterior descending artery.

[0106] 10. The ostium of an angulated vein graft origin.

[0107] 11. Any of many of the above locations in conjunction withinvolvement of the bifurcation and an alternate vessel.

[0108] The proximal angled stent of the present invention typically canbe used as a solo device to treat the foregoing indications, or it canbe used in conjunction with the main vessel stent described herein forstenting the bifurcation.

[0109] In keeping with the invention, as depicted in FIGS. 6A and 6B,main-vessel stent 20 is configured for deployment in main-vessel 6.Main-vessel stent 20 includes cylindrical member 21 having distal end 22and proximal end 23. Main-vessel stent 20 includes outer wall surface 24which extends between distal end 22 and proximal end 23 and incorporatesaperture 25 on outer wall surface 24. Aperture 25 is configured so that,upon expansion, it approximates the diameter of expanded proximal end 14of proximal angled stent 10. When main-vessel stent 20 is implanted andexpanded into contact with main-vessel 6, aperture 25 is aligned withside-branch vessel 5 and proximal end 14 of proximal angled stent,thereby providing an unrestricted blood flow path from the side-branchvessel to the main vessel. Unlike the prior art, the main-vesselcatheter allows selection and positioning of an aperture at theside-branch ostium. Furthermore, it provides for the positioning of aguide wire during main-vessel stent deployment which can be used foradditional intervention if necessary. In the prior art techniques accessto a side-branch is through a randomly selected stent element (“cell”)and is only possible after deployment of the stent. The precisepositioning of aperture 25 is optional and aperture 25 could bepositioned either closer to the proximal or distal end of stent 20.

[0110] Proximal angled stent 10 and main-vessel stent 20 can be formedfrom any of a number of materials including, but not limited to,stainless steel alloys, nickel-titanium alloys (the NiTi can be eithershape memory or pseudoelastic), tantalum, tungsten, or any number ofpolymer materials. Such materials of manufacture are known in the art.Further, proximal angled stent 10 and main-vessel stent 20 can havevirtually any pattern known to prior art stents. In one configuration,proximal angled stent 10 and main-vessel stent 20 are formed from astainless steel material and have a plurality of cylindrical elementsconnected by connecting members, wherein the cylindrical elements havean undulating or serpentine pattern. Such a stent is disclosed in U.S.Pat. No. 5,514,154 and is manufactured and sold by AdvancedCardiovascular Systems, Inc., Santa Clara, Calif. The stent is soldunder the trade name MultiLink® Stent. Such stents can be modified toinclude the novel features of proximal angled stent 10 (the angulation)and main-vessel stent 20 (the aperture).

[0111] Proximal angled stent 10 and main-vessel stent 20 preferably areballoon-expandable stents that are mounted on a balloon portion of acatheter and crimped tightly onto the balloon to provide a low profiledelivery diameter. After the catheter is positioned so that the stentand the balloon portion of the catheter are positioned either in theside-branch or the main vessel, the balloon is expanded, therebyexpanding the stent beyond its elastic limit into contact with thevessel. Thereafter, the balloon is deflated and the balloon and catheterare withdrawn from the vessel, leaving the stent implanted. Deploymentof the angled and main-vessel stents is accomplished by a novel stentdelivery system adapted specifically for treating bifurcated vessels.The proximal angled stent and the main-vessel stent could be made to beeither balloon expandable or self-expanding.

[0112] In one embodiment for delivering the novel stents of the presentinvention, as depicted in FIGS. 7A and 7B, side-branch stent deliveryassembly 30 is provided and includes side-branch catheter 31. Theside-branch catheter includes distal end 32 which is configured fordelivery in the patient's vasculature and proximal end 33 which remainsoutside the patient. First guide wire lumen 34A extends through at leasta portion of side-branch catheter 31 depending on the type of catheterdesired for a particular application. First guide wire lumen 34Apreferably is defined by distal end 34B and side port 34C, which istypical of the so-called rapid-exchange-type catheters. Typically, aslit (not shown) extends from side port 34C to just proximal of theballoon portion of the catheter so that the catheter can be rapidlyexchanged during a medical procedure, as is known.

[0113] The expandable member 35, which is typically a non-distensibleballoon, has a first compressed diameter for delivery through thevascular system, and a second expanded diameter for implanting a stent.The expandable member 35 is positioned near distal end 32, and in anyevent between distal end 32 of first catheter 31 and side port 34C.

[0114] Referring to FIGS. 7A and 7B, tracking guide wire 36A, distal end36B, and proximal end 36C all extend through first guide wire lumen 34A.Tracking guide wire 36A preferably is a stiff wire having a diameter of0.014 inch, but can have a different diameter and stiffness as requiredfor a particular application. A particularly suitable guide wire caninclude those manufactured and sold under the trade names Sport® andIronman®, manufactured by Advanced Cardiovascular Systems, Inc., SantaClara, Calif. Tracking guide wire 36A is sized for slidable movementwithin first guide wire lumen 34A.

[0115] Stent delivery assembly 30 further includes second guide wirelumen 39A which is associated with expandable member 35. Second guidewire lumen 39A includes angle portion 39B and straight portion 39C, andis firmly attached to outer surface 40 of catheter 31, at a point justproximal to expandable member 35. Integrated stent-positioning guidewire 41A is sized for slidable movement within second guide wire lumen39A. A slit 39D is formed in lumen 39A near its distal end so that thestiff guide wire 41A can bow outwardly as shown in FIG. 7B. The portionof guide wire 41A that bows out of slit 39D will limit the advancementof catheter 31 as will be further described infra. Integratedstent-positioning guide wire 41A has distal end 41B, and proximal end41C which extends out of the patient. Again, it is preferred thatintegrated stent-positioning guide wire 41A be a fairly stiff wire aspreviously described, for the reasons set forth below in delivering andimplanting the stents in the bifurcation.

[0116] In an alternative embodiment, catheter 31 can have an angledexpandable member 42 as depicted in FIG. 8. The proximal end of theexpandable member is angled to coincide with the angle of proximalangled stent 10 (not shown in FIG. 8 for clarity). This embodiment isparticularly useful in delivering the angled stent since the secondguide wire lumen 39A, and its angled portion 39B, have the same angle asthe stent and the proximal end of the expandable member.

[0117] In further keeping with the invention, as depicted in FIGS.9A-11D, proximal angled stent 10 is mounted on side-branch catheter 31and implanted in side-branch vessel 5. The method of achieving proximalangled stent implantation is as follows.

[0118] In keeping with the method of the invention, proximal angledstent 10 first is tightly crimped onto expandable member 35 forlow-profile delivery through the vascular system.

[0119] In one embodiment of the side-branch catheter system 30(side-branch catheter plus proximal angled stent), distal end 36B ofguide wire 36A is advanced into side-branch vessel 5 and distal to thetarget area, with proximal end 36C remaining outside the patient. Theside-branch catheter 31 is then advanced within a guiding catheter (notshown) along tracking guide wire 36A until distal end 32 of the catheteris just proximal (about 1 cm) from entering side-branch vessel 5. Up tothis point, guide wire 41A resides in second guide wire lumen 39A sothat distal end 41B of the wire preferably is near, but not in, angledportion 39B of guide wire lumen 39A. This method of delivery preventsthe two guide wires from wrapping around each other, guide wire 41Abeing protected by the catheter during delivery. The distal end 41B ofintegrated stent positioning guide wire 41A is then advanced by havingthe physician push proximal end 41C from outside the body. The distalend 41B of the integrated stent-positioning guide wire travels throughguide wire lumen 39A and angled portion 39B and passes close to proximalend 14 of angled stent 10 and expandable member 35 and exits lumen 39B.As guide wire 41A is advanced into, through and out of lumen 39B, thestiffness of the wire causes it to bow outwardly through slit 39D in thedistal portion of lumen 39A. Thus, as can be seen for example in FIGS.9B, 10A, 10B, and 11B-11D, the positioning guide wire bows outwardly anddue to its stiffness, provides a bumper against the ostium of theside-branch vessel to assist in positioning and deploying the stents.The stent-positioning guide wire 41A is advanced in the main vesseluntil distal end 41B is distal to side-branch vessel 5. The catheter isthen advanced into side-branch vessel 5 until resistance is felt fromthe stent-positioning guide wire 41A pushing up against the ostium ofside-branch vessel 5. As previously described, stent-positioning wire41A is relatively stiff, as is tracking guide wire 36A, so that they canproperly orient side-branch catheter 31 as it is advanced intoside-branch vessel 5. Angled portion 39B of second guide wire lumen 39Ais angled to assist in rotating the side-branch catheter into properposition into the side-branch vessel. If the stent approachesside-branch vessel 5 in the incorrect position, as depicted in FIGS.11A-11D, stent-positioning wire 41A would be forced to make a very acuteangle. The wire stiffness, however, prevents this from happening andcauses the wire to assume the position of least stress. To relieve thisstress buildup, wire 41A creates a torque on angled portion 39B causingguide wire lumen 39A and side-branch catheter 31, with proximal angledstent 10, to rotate into the correct position. Preferably, slit 39D isformed on catheter 31 outer surface near angled portion 39B so thatstent-positioning guide wire 41A can bow outwardly out of slit 39Dthereby increasing the ability to torque the catheter and the proximalangled stent.

[0120] Thereafter, proximal angled stent 10 mounted on the expandablemember 35 is aligned across the target area, and viewed underfluoroscopy, the acute angle 18 on the proximal end of the proximalangled stent is aligned at the intersection of side-branch vessel 5 andmain-vessel 6 (the ostium of the side-branch vessel) so that theproximal angled stent completely covers the target area in side-branchvessel 5, yet does not extend into the main-vessel 6, therebycompromising blood flow. The expandable member 35, which is typically anon-distensible balloon, is expanded by known methods, thereby expandingthe proximal angled stent into contact with side-branch vessel 5, andthereby implanting the proximal angled stent in the side-branch vessel.Thereafter, expandable member 35 is deflated and side-branch catheterassembly 31 is withdrawn from the patient's vasculature. The side-branchcatheter 31 is designed so that both tracking guide wire 36A andstent-positioning guide wire 41A can be left in their respective vesselsshould sequential or simultaneous high pressure balloon inflation berequired in each of the vessels in order to complete the stentingprocedure. In other words, the integrated positioning wire can beunzipped through the slit (not shown) from the proximal 100 cm of thecatheter thereby allowing it to act as a rapid exchange wire.Preferably, high pressure balloons are inflated simultaneously in themain vessel and proximal angled stents in order to avoid deforming onestent by unopposed balloon inflation within the other one. Thisadditional step is a matter of physician choice. Utilizing this method,side-branch vessel 5 can be stented without the need for stenting themain vessel, as shown in FIGS. 11A-11D.

[0121] If necessary, main-vessel 6 also can be stented after stentingthe side-branch vessel. In that regard, and in keeping with theinvention, main-vessel catheter assembly 50 is provided for implantingmain-vessel stent 20, as depicted in FIGS. 12A to 13E. In oneembodiment, as shown in FIGS. 12A-12C, main-vessel catheter 50 includesdistal end 51 which is configured for advancement within the patient'svasculature, and proximal end 52 which remains outside the patient. Themain-vessel catheter includes guide wire lumen 53A having distal end 53Band side port 53C, which is proximal to the balloon portion of thecatheter. Side port 53C is provided in a so-called rapid-exchangecatheter system which includes a slit (not shown) as is known in theart. Expandable member 54 is located near distal end 51 of main-vesselcatheter 50. Typically, expandable member 54 is a non-distensibleballoon of the type known in the art for delivering and expandingstents.

[0122] In further keeping with the invention, positioning guide wirelumen 55A is positioned partly on the catheter shaft and partly onexpandable member 54, and is configured for slidably receivingintegrated stent-positioning guide wire 56A. Prior to stent delivery,guide wire 56A resides in guide wire lumen 55A and only during stentdelivery is it then advanced into and through angled portion 55B of thelumen.

[0123] Other embodiments for implanting main-vessel stent 20 inmain-vessel 6 are depicted, for example, in FIGS. 12D-12F. Thisembodiment is identical to that depicted in FIGS. 12A-12C, with theaddition of ramp 57 which is mounted on balloon 54 and provides a slightincline for guide wire 56A as it exits guide wire lumen 55A. As theguide wire slides along ramp 57, distal portion 56B of the guide wirewill move radially outwardly which helps position the guide wire andorient it into the side-branch vessel. In another embodiment forimplanting the main-vessel stent in the main vessel, as depicted inFIGS. 12G-12I, guide wire lumen 55A passes underneath main-vessel stent20 and on top of balloon 54. The distal end 55B curves along the balloonso that as guide wire 56B advances out of the distal end 55B of thelumen, it is travelling radially outwardly so that it can more easilylocate and advance into the side-branch vessel 5.

[0124] In still another embodiment for implanting main-vessel stent 20in the main-vessel 6, as depicted in FIGS. 12J-12L, guide wire lumen 55Ais positioned under stent 20 and terminates at distal end 55B in themiddle of aperture 25. The distal end 55B of the guide wire lumen willspring outwardly which facilitates advancing guide wire distal end 41Binto the side branch vessel. A distal guide wire lumen 58 is attached tothe balloon 35 outer surface and extends from aperture 25 to essentiallythe distal end of the catheter.

[0125] In one method of implanting main-vessel stent 20 in main-vessel6, as depicted in FIGS. 12A-12I and 13A-13D, guide wire 41A remains inposition in main-vessel 6, while the side-branch guide wire 36A iswithdrawn from the patient. Main-vessel catheter 50 is backloaded ontoguide wire 41A by inserting proximal end 41C of the wire into the distalend of the catheter and into guide wire lumen 53A. Main-vessel catheter50 is advanced over guide wire 41A and viewed under fluoroscopy untilmain-vessel stent 20 is positioned in main-vessel 6, just proximal toside-branch vessel 5. The distal end 56B of the integratedstent-positioning guide wire 56A is then advanced by the physicianpushing on proximal end 56C from outside the body. The distal end 56B ofwire 56A advances into and through positioning guide wire lumen 55A andpasses underneath the proximal end of the main-vessel stent 20 and exitsthe angled portion 55B of the lumen and enters side-branch vessel 5. Themain-vessel catheter 50 is then advanced distally into the main vesseluntil resistance is felt from the stent-positioning guide wire 56Apushing up against the ostium of the side-branch vessel. The stiffnessof stent-positioning guide wire 56A causes the main-vessel catheter 50,with main-vessel stent 20 thereon, to rotate so that aperture 25 isfacing the side-branch vessel 5 ostium and proximal angled stent 10already implanted.

[0126] Expandable member 54, which is typically a non-distensibleexpandable balloon, is inflated thereby expanding main-vessel stent 20into contact with main-vessel 6. Aperture 25 correspondingly expands andwhen properly aligned, provides a blood flow path between aperture 25and proximal angled stent 10 implanted in side-branch vessel 5. As canbe seen in FIGS. 12A-12I and 13A-13D, positioning guide wire lumen 55Ais positioned on expandable member 54, such that when the expandablemember is inflated, positioning guide wire lumen 55A does not interferewith implanting main-vessel stent 20. After the main-vessel stent isimplanted in the main vessel, expandable member 54 is deflated, andmain-vessel catheter 50 withdrawn from the patient. As seen in FIG. 14,the bifurcated vessel has been fully covered by the stents, side-branchvessel 5 is covered by proximal angled stent 10, and main-vessel 6 iscovered by main-vessel stent 20, so that no portion of bifurcation 4 isleft uncovered and there is no overlap in the implanted stents.

[0127] In an alternative method of implanting main-vessel stent 20 inmain-vessel 6 as depicted in FIGS. 12J-12L, tracking guide wire 41A isadvanced through guide wire lumen 55A and guide wire lumen 58 so that itadvances distally of the distal end 51 of the catheter. Thus, guide wiredistal end 41B is advanced into the main vessel so that it is distal ofthe side-branch vessel. Guide wire 56A, which until this point hasremained within guide wire lumen 53A (see FIG. 12K), is advanceddistally as depicted in FIG. 12L and advanced into the main vesseldistally of the side-branch vessel. Guide wire 41A is then withdrawnproximally through guide wire lumen 58 until guide wire distal end 41Bis able to exit guide wire lumen distal end 55B, as shown in FIG. 12L.Since guide wire lumen 55B is preformed and has bias, it will springoutwardly. Guide wire 41A can then be advanced into the side-branchvessel for further positioning. As the catheter 50 is advanced over theguide wires, distal portion 41B of the guide wire will push against theostium of the side-branch vessel thereby insuring the location ofmain-vessel stent 20, and importantly aperture 25 will align with theopening to the side-branch vessel 5.

[0128] A non-angulated stent (see FIG. 15) can be implanted using thecatheter system of FIGS. 7A-11D for stenting a side-branch vessel havingan origin approaching 90° in its takeoff from the main vessel. In thiscircumstance the positioning wire serves solely to arrest the forwardmovement of the stent precisely at the origin of the vessel for moreprecise positioning. However, acute angle 18 is appropriate for abifurcated vessel 4 in which the angulation is acute angle 18, or lessthan 90°. Thus, consideration could be given to standard 30°, 45°, and60° angled stent designs for proximal angled stent 10, which shouldprovide sufficient luminal wall coverage when keeping with the presentinvention. Proximal angled stent 10 has a wide range of applicabilityand can be used for stenting ostial side-branch lesions, ostialcircumflex or left anterior descending (LAD) lesions where thebifurcation is an acute angle, or less than 90°, and ostial lesionsinvolving the angulated origin of a right coronary or vein graft.Importantly, the stents of the present invention provide full coverageof the ostial intima without protruding into the main vessel or withoutcompromising subsequent access to the distal portion of the main vessel.

[0129] In order to assist in properly aligning both proximal angledstent 10 and main-vessel stent 20 in side-branch vessel 5 andmain-vessel 6, respectively, positioning guide wire lumen 39A, onside-branch catheter 31, and guide wire lumen 55A, on main-vesselcatheter 50, can be radiopaque, or have a radiopaque marker associatedtherewith so that they are visible under fluoroscopy. Thus, whenadvancing side-branch catheter 31 and main-vessel catheter 50, theproper orientation can be more easily determined by viewing the positionof positioning guide wire lumen 39A in connection with main-vessel 6 orpositioning guide wire lumen 55A in connection with aligning aperture 25with side-branch vessel 5. Additionally, positioning guide wire 56A forpositioning main-vessel stent 20 and positioning guide wire 41A forpositioning angled stent 10 are either radiopaque or have radiopaqueportions, such as gold markers, to assist in positioning and orientingthe catheters and stents during implantation and deployment.

[0130] While the foregoing description includes implanting proximalangled stent 10 in side-branch vessel 5 prior to implanting main-vesselstent 20 in main-vessel 6, in an alternative embodiment, the implantingprocedure can be reversed. However, it should be understood that byimplanting main-vessel stent 20 in main-vessel 6, and subsequentlyimplanting proximal angled stent 10 in side-branch vessel 5, aperture 25must be carefully aligned with side-branch vessel 5 so that side-branchcatheter 31 can be advanced through expanded main-vessel stent 20 andaperture 25 and into side-branch vessel 5 for implanting proximal angledstent 10.

[0131] While side-branch catheter 31 and main-vessel catheter 50 havebeen described herein as being of the rapid-exchange type, they also canbe of a conventional over-the-wire-type catheter. In over-the-wire-typecatheters, the guide wire lumen extends from the distal end of thecatheter to the proximal end with no side port as is found in therapid-exchange-type catheters. Typical of over-the-wire-type cathetersis the type disclosed in U.S. Pat. Nos. 4,323,071 and B1 4,323,071,which are incorporated herein by reference, and are commonly assignedand commonly owned by Advanced Cardiovascular Systems, Inc., SantaClara, Calif.

[0132] In one embodiment of the invention, as depicted in FIG. 15,main-vessel unmodified stent 60 can be configured without the sideaperture 25 of stent 20. Upon expansion, the individual strut members 61of unmodified stent 60 expand sufficiently to permit a balloon catheterto be inserted therethrough, and expanded, to form an aperture whichcorresponds to the opening to side-branch vessel 5.

[0133] In one method of stenting the bifurcation, side-branch vessel 5is first stented as described, for example, in the manner shown in FIGS.9A through 11D. Thereafter, main-vessel 6 is stented with unmodifiedmain-vessel stent 60, which does not have an aperture formed in the sideof the stent. As shown in FIGS. 15-18, unmodified stent 60 is mounted onexpandable portion 54 of main-vessel catheter 50. Main-vessel catheter50 is backloaded onto the proximal end of guide wire 41A which isalready in position in the main vessel. Main-vessel catheter 50 isadvanced over the guide wire and viewed under fluoroscopy until stent 60is positioned in the main vessel about one cm proximal to theside-branch vessel. The distal end 56B of integrated stent-positioningguide wire 56A is then advanced by the physician by pushing the proximalend 56C from outside the body. The distal end 56B of wire 56A travelsthrough guide wire lumen 55A and passes underneath the proximal end ofunmodified stent 60 and exits the angled end of the lumen 55B and entersside-branch vessel 5. The main-vessel catheter 50 is then advanceddistally into the main vessel until resistance is felt from thestent-positioning guide wire 56A pushing up against the ostium ofside-branch vessel 5. The stiffness of stent-positioning guide wire 56Acauses the main-vessel catheter 50 with unmodified stent 60 to rotate soa stent cell 62 is precisely facing the side-branch vessel 5 ostium.Expandable member 54 is expanded by known means so that unmodified stent60 expands into contact with main-vessel 6. Expandable member 54 is thendeflated, catheter 50 is withdrawn from the patient's vascular system,leaving guide wire 56A in the side branch.

[0134] At this point, proximal angled stent 10 is implanted in theside-branch vessel and unmodified main-vessel stent 60 is implanted andextends across side-branch vessel 5. In order to provide an opening inunmodified main-vessel stent 60 that aligns with the opening to theside-branch vessel, third catheter 65, which can be a standard PTCAcatheter, is backloaded onto guide wire 56A, already in side-branchvessel 5, and advanced within the patient's vascular system over theguide wire. As shown in FIG. 18, distal end 66 of catheter 65 isadvanced over guide wire 56A until the distal end 66 of catheter 65begins to pass through cell 62 of unmodified main-vessel stent 60 andenter side-branch vessel 5. Catheter 65 can be of a known type used inangioplasty, as described above, having a non-distensible member orballoon 67. Once balloon 67 is positioned through stent cell 62 and inthe opening of side-branch vessel 5, it is expanded, thereby expandingsome of struts 61 comprising unmodified stent 60 and forming asubstantially circular opening from main-vessel 6 through unmodifiedstent 60 and into side-branch vessel 5. In essence, balloon 67 spreadsapart some of the struts of unmodified stent 60 to form an opening instent 60 that corresponds to the opening to side-branch vessel 5,thereby providing a clear blood flow path between the main vessel andthe side-branch vessel.

[0135] Unmodified main-vessel stent 60 is positioned such that itcrosses the opening to side-branch vessel 5. As set forth above, aparticularly well suited stent for this embodiment includes a stentdistributed under the trade name MultiLink® Stent, manufactured byAdvanced Cardiovascular Systems, Inc., Santa Clara, Calif. By implantingunmodified main-vessel stent 60 in main-vessel 6 with an appropriatestent cell precisely aligned with the side-branch ostia, dilatationthrough this same cell over wire 56A assures a fully expanded andnon-distorted cell at the ostium of side-vessel 5.

[0136] In an alternative embodiment, as shown in FIGS. 19A-19C,unmodified stent 60 is implanted first, then the side-branch proximalangled stent 10 is implanted. In one method of deploying unmodifiedstent 60, the unmodified stent 60 can be mounted on expandable portion54 of main-vessel catheter 50. Main-vessel catheter 50 is backloadedonto the proximal end of guide wire 41A. Main-vessel catheter 50 isadvanced over guide wire 41A and viewed under fluoroscopy untilunmodified stent 60 is positioned in main-vessel 6, proximal toside-branch vessel 5. The distal end of the integrated stent-positioningguide wire 56B is then advanced by the physician pushing the proximalend 56C from outside the body. The distal end 56B of wire 56A travelsthrough second guide wire lumen 55A and passes underneath the proximalend of unmodified stent 60 and exits the angled end of the lumen 55B andenters side-branch vessel 5. The main-vessel catheter 50 is thenadvanced distally into the main vessel until resistance is felt from thestent-positioning guide wire 56A pushing up against the ostium of theside-branch vessel 5. The stiffness of stent-positioning guide wire 56Acauses the main-vessel catheter 50 with unmodified stent 60 to rotate soa stent cell 62 is precisely facing the side-branch vessel 5 ostium.Expandable member 54 is expanded by known means so that unmodified stent60 expands into contact with main-vessel 6. Expandable member 54 is thendeflated, and catheter 50 is withdrawn from the patient's vascularsystem, leaving guide wire 56A in side branch 5.

[0137] In further keeping with the method of stenting, as shown in FIG.19B, third catheter 65, which can be a standard PTCA catheter, isbackloaded onto guide wire 56A already in side-branch vessel 5 andadvanced within the patient's vascular system over the guide wire.Distal end 66 of catheter 65 is advanced over guide wire 56A until thedistal end 66 of the catheter begins to pass through struts 61 of stentcell 62 of unmodified main-vessel stent 60 and enter side-branch vessel5. Catheter 65 can be of a known type used in angioplasty, as describedabove, having a non-distensible member or balloon 67. Once balloon 67 ispositioned through a stent cell 62 the opening of side-branch vessel 5,it is expanded, thereby expanding some of the struts comprisingunmodified stent 60 and forming a substantially circular opening frommain-vessel 6 through unmodified stent 60 and into side-branch vessel 5.In essence, balloon 67 spreads apart the struts 61 of unmodified stent60 to form an opening in the unmodified stent that corresponds to theopening to side-branch vessel 5, thereby providing a clear opening forfurther stenting side-branch vessel 5.

[0138] With the main vessel now stented as depicted in FIGS. 19A-19C,side-branch vessel 5 is stented in the same manner as described in FIGS.9-11. The only difference is that in FIG. 19, unmodified main-vesselstent 60 already is implanted when catheter 31 is advanced intoside-branch vessel 5. Side-branch catheter 31 is backloaded onto guidewire 36A already in side-branch vessel 5. Side-branch catheter 31 isthen advanced until the distal tip of side-branch catheter 31 justenters the side-branch vessel 5 ostium. The distal end 41B of theintegrated guide wire 41A is then advanced by the physician pushing theproximal end 41C from outside the body. The distal end 41B of theintegrated stent-positioning guide wire travels through second guidewire lumen 39A and angled portion 39B and passes close to the proximalend of proximal angled stent 10 and expandable member 35 and exits lumen39B. The stent-positioning guide wire 41A is advanced until the distalend 41B is distal to side-branch vessel 5. The catheter is then advancedinto the side-branch vessel until resistance is felt from thestent-positioning guide wire 41A pushing up against the ostium of theside-branch vessel. As previously described, stent-positioning wire 41Ais relatively stiff, as is tracking guide wire 36A, so that they canproperly orient side-branch catheter 31 as it is advanced into theside-branch vessel. Angled portion 39B of second guide wire lumen 39A isangled to assist in rotating the side-branch catheter into properposition into side-branch vessel 5. If the stent approaches theside-branch vessel in the incorrect position, the stent-positioning wire41A would be forced to make a very acute angle. The wire stiffness,however, prevents this from happening and causes the wire to assume theposition of least stress. To relieve this stress buildup, wire 41Acreates a torque on angled portion 39B causing guide wire lumen 39A andside-branch catheter 31 with proximal angled stent 10 to rotate into thecorrect position. Once the proximal angled stent is positioned inside-branch vessel 5, expandable member 35 is expanded so that theproximal angled stent expands into contact with side-branch vessel 5,making sure that proximal end 14 of proximal angled stent 10 covers andis aligned with the side-branch vessel 5 at bifurcation 4. Proximal end14 is aligned so that it coincides with acute angle 18, thereby ensuringthat all portions of side-branch vessel 5 are covered by the proximalangled stent, where side-branch vessel 5 meets main-vessel 6. Anunobstructed blood-flow path now exists between expanded unmodifiedstent 60 and main-vessel 6 through the opening previously formed andinto side-branch vessel 5 and through implanted proximal angled stent10.

[0139] Prior art devices that have attempted to first stent the mainvessel and randomly select a stent cell to expand for alignment with theside-branch vessel, have generally failed. One such approach, known asthe “monoclonal antibody” approach, as depicted in FIGS. 19D and 19E,depict what can happen when an inappropriate target stent cell isselected randomly and then expanded by a high pressure balloon. As shownin FIG. 19D, which is a view looking down side-branch vessel 5 incross-section at a prior art stent 68, the physician randomly selectsstent cell 69 which is a sub-optimal cell to expand with the balloonportion of a catheter. As depicted in FIG. 19E, after balloon expansionin the suboptimal cell 69, entry into the cell with a catheter may beimpossible or, if accomplished, expansion of the balloon may beincomplete. The aperture created will be inadequate and major distortionin the adjacent stent struts may occur. Consequences may includesubacute thrombosis or restenosis. With the present invention, as shownin FIGS. 19A-19C, the target stent cell 62 is the optimal cell forexpansion, and is preselected with a wire in place before stentdeployment (that same wire remaining in place for subsequent access),and is oriented optimally with respect to the side-branch ostium priorto deployment. The resulting expansion as shown in FIG. 19F, guaranteesan optimal aperture where the stent struts have been expanded providinga blood flow path from the main vessel to the side-branch vessel.

[0140] In another alternative embodiment for stenting a bifurcation, asdepicted in FIGS. 20A-20C, main-vessel catheter 70 includes expandablemember 71 near its distal end, while the proximal end of the catheter(not shown) is similar to those previously described and can be eitherof the rapid-exchange or over-the-wire types. Catheter 70 includestracking guide wire lumen 72 for slidably receiving tracking guide wire73, lumen 72 extending at least partially through the catheter in therapid-exchange configuration and all the way through the catheter in theover-the-wire configuration. The catheter also includes a positioningguide wire lumen 74 that is associated with the catheter outer surfaceand extends onto and is attached to at least a portion of expandablemember 71. As shown in FIG. 20A, positioning guide wire lumen 74 extendsalong the expandable member and ends just at the distal taper of theexpandable member. As depicted in FIGS. 20B and 20C, positioning guidewire lumen 74 can be formed of two sections, namely distal section 75attached to the distal tip of the catheter, and proximal section 76extending along and attached to the expandable member and the catheter.As previously described, guide wires 73,77 are intended to be relativelystiff wires so that they can more easily maneuver the catheter. In theseembodiments, stent 78 is mounted on the expandable member and overpositioning guide wire lumen 74. Positioning guide wire 77 is configuredfor slidable movement within positioning lumen 74.

[0141] In one method of stenting a vessel just proximal to a bifurcationusing main-vessel catheter 70, tracking guide wire 73 is firstpositioned within the main vessel as previously described. The catheteris then backloaded onto the guide wire by inserting the wire into thetracking guide wire lumen 72 and advancing the catheter into thepatient's vascular system. At this point, positioning guide wire 77resides within positioning guide wire lumen 74 and is carried into themain vessel where it will be released and advanced. Once the catheterhas reached the target area, positioning guide wire 77 is advanceddistally out of the positioning guide wire lumen (for FIG. 20A) orpulled back slightly out of distal section 75 of the positioning guidewire lumen (for FIGS. 20B and 20C). Once released by removal of theguide wire, distal section 75 will spring out so that the positioningguide wire can seek out and be advanced into the side-branch vessel.Once the positioning guide wire is advanced in the side-branch vessel,the catheter is again advanced and the stent is implanted in the mainvessel in a manner similar to that described for other embodiments. Thecatheter of FIGS. 20A-20C is designed to allow deployment of a stentvery near but not “snowplowing” a bifurcation or side branch and isconfigured for treating bifurcations as depicted in FIGS. 23A-25B. Acommonly encountered situation in which catheter 70 would be used is anLAD that has disease right at and proximal to the diagonal take-off.After a careful look at multiple views, the physician should beconvinced that the diagonal is spared, but the lesion is very close andor immediately adjacent to the diagonal take-off, as shown in FIG. 20D.It is very difficult to position a standard stent in the LAD and becertain that the lesion is fully covered and the diagonal is notsnowplowed or jailed. The catheter 70, having one wire in the LAD (mainvessel) and the other in the diagonal (side-branch vessel), would allowprecise definition of the bifurcation and avoid these problems. Squarestent 78A, which has both ends transverse to the stent axis, could bedeployed just proximal to the carina, in which case the stent distal endmay need to be flared a bit, or more likely, relaxed back to where thepositioning guide wire 77 is resting against the proximal aspect of theostium, visually defining the ostium in relationship to the stent andallowing precise deployment.

[0142] Several alternative embodiments of main-vessel catheter 70 shownin FIG. 20A, are depicted in FIGS. 20E, 21 and 22. The catheter deviceshown in FIG. 20E is similar to that shown in FIG. 20A, with theexception that ramp 57 is employed just distal of the distal end of theguide wire lumen 74 so that as guide wire 77 exits the lumen, it willmove outwardly along ramp 57 so that it more easily advances into theside-branch vessel. Likewise, as shown in FIGS. 21 and 22, which aresimilar to the catheter described and depicted in FIGS. 20B and 20C, itis intended that guide wire 77 move outwardly so that it can more easilybe advanced into the side-branch vessel. In that regard, the distal endof guide wire lumen 74 is biased outwardly as shown in FIG. 22, so thatas the guide wire 77 is pulled back from lumen 75, the distal end ofguide wire lumen 74 will spring outwardly thereby assisting guide wire77 in moving radially outwardly to be positioned in the side-branchvessel.

[0143] In order to implant a square main-vessel stent 78A in a mainvessel, where the disease is at or just proximal to the side-branchvessel, catheter 70 as depicted in FIGS. 21 and 22 is well suited. Forexample, catheter 70 is advanced over wire 77 until the catheter ispositioned just proximal of the side-branch vessel. Guide wire 73, whichup to this point has been contained within catheter 70, is advanced intothe main vessel so that it is distal of the side-branch vessel. Guidewire 77 is then withdrawn proximally so that its distal end 77A iswithdrawn from lumen 75, whereupon wire 77 and the distal end of guidewire lumen 74 spring outwardly thereby assisting the positioning ofguide wire 77 into the side-branch vessel. The wire is then advancedinto the side-branch vessel and catheter 77 is advanced so that wire 77rests on the proximal ostium of the side-branch vessel, wherein squarestent 78A can then be expanded to cover the diseased portion, but notspan or cover (jail) the opening to the side-branch vessel.

[0144] If the diseased portion of a main vessel is directly adjacent theopening to the side-branch vessel, as depicted in FIG. 20F then thecatheter system as depicted in FIG. 20A can be incorporated only itwould implant distal angled stent 78B. As shown in FIG. 20F, stent 78Bhas an angle at its distal end which coincides with the opening to theside-branch vessel so that the diseased portion of the main vessel iscovered by the distal end of the stent, with the angle of the stentangled proximally so that the side-branch vessel is not covered orjailed. Various alternatives of square stent 78A and distal angled stent78B are used for treating various conditions as depicted in FIGS. 23Athrough 26B.

[0145] In another alternative embodiment as depicted in FIGS. 27-33, adual balloon Y-shaped catheter assembly is provided to stent abifurcation. In this embodiment, a Y-shaped stent is implanted to coverthe bifurcation. Catheter 90 includes first and second expandablemembers 91,92 that are configured to reside side by side (Y-shaped) forlow profile delivery and to spring apart for implanting the stents.Locking ring 93 may be used to assist in holding the expandable memberstogether until just prior to use, at which time it is removed. A guidewire lumen 95 extends at least through a portion of the catheter andslidably receives guide wire 96. Guide wire lumen 98 extends at leastthrough a portion of the catheter and slidably receives guide wire 99.Guide wire lumen 98 includes distal section 98A and 98B. A Y-shapedstent 100 is mounted on the first and second expandable members 91, 92.

[0146] In one method of stenting the bifurcated vessels, as shown inFIGS. 29 to 33, guide wire 99, previously positioned distal to thebifurcation in one limb (perhaps the most vulnerable to problems forwire recrossing), is back loaded into lumens 98A and 98B and catheter 90is advanced over wire 99 so that the catheter is advanced distallybeyond the bifurcation. Guide wire 96 which has been contained in lumen95 to this point, is carried in lumen 95 as the catheter is advancedalong guide wire 99. Wire 99 is then withdrawn until its distal endpulls out of the distal section 98A. As guide wire 99 is pulled back(proximally), the first and second expandable members 91,92, which arenormally biased apart, are released and now spring apart. The wire whoselumen is most distant (lateral) to the bifurcation (in this case wire96) is then advanced into the distal vessel and the other wire (in thiscase 99) withdrawn as seen in FIG. 29B. The catheter is then withdrawnproximally so that the expandable members 91,92 are now proximal to thebifurcation as depicted in FIG. 29C and the other guide wire (in thiscase wire 99) advanced into the other limb of the bifurcation as shownin FIG. 30. Catheter 90 is then advanced distally over both guide wires96 and 99, as shown in FIG. 31, until stent 100 is positioned in thebifurcation of the intersection of the vessels 105,106. Due to theappropriate wire selection, rotation of no more than 90° will berequired. Stent 100 is implanted by inflating expandable members 91,92in a known manner. The expandable members are then deflated, and thecatheter is withdrawn from the patient. The novel arrangement of guidewires 96 and 99 and their respective lumens permit single unit transportof a Y stent to the distal target site without wire wrapping problemsand it allows for minimal requirements of rotation of the device (lessthan 90°) for optimal deployment (allowing minimal twist deformity). Theguide wires may be left in place for further intervention such asfinishing the stents with simultaneous high pressure balloon inflation.

[0147] Referring to FIGS. 37-41, in yet another alternative embodiment,the dual balloon Y-shaped catheter assembly may include a restrainingmember such as mandril 120. The mandril is positioned within lumens 98Aand 98B. It is also contemplated that an assembly can be used having twoseparate balloons that inflate simultaneously. The mandril should bestiff enough to secure expandable members 91,92 to each other. Themandril may extend distally of expandable member 92 and have anatraumatic distal tip. Alternatively, it is contemplated that lumen 98Acan be sealed at its distal end. If desired, locking ring 93 can be usedto assist in holding the expandable members together until just prior touse, at which time it is removed.

[0148] In use, guide wire 96, previously positioned distal to thebifurcation in one limb, is back loaded into lumen 95 and catheter 90 isadvanced over wire 96 so that the catheter is advanced to a locationproximate the bifurcation. The mandril 120 is carried in lumens 98A and98B as the catheter is advanced along guide wire 96. When the catheterreaches the bifurcation, the mandril 120 can be withdrawn until itsdistal end pulls out of distal section 98A. As the mandril is retracted(proximally), expandable members 91,92, which are normally biased apart,are released and spring apart, as illustrated in FIG. 39. The mandril120 may now be removed from the patient and guide wire 122 inserted intolumen 98B. The guide wire 122 may then be advanced into the other limbof the bifurcation as shown in FIG. 40. Alternatively, the mandril maybe a guide wire or guide wire-like element, and may itself be advancedinto the limb, thus eliminating the need for guide wire 122.

[0149] Catheter 90 is then advanced distally over guide wire 96 andguide wire 122 (or mandril 120), until stent 100 is properly positionedin the bifurcation. Stent 100 is implanted by inflating expandablemembers 91,92 in a known manner. The expandable members are thendeflated, and the catheter is withdrawn from the patient.

[0150] In an alternative embodiment of the invention, a pair of stentshaving varying stent cell density are implanted in a bifurcated vessel,as depicted in FIGS. 34-36C.

[0151] As shown in FIG. 34, apertured stent 115 is provided in whichaperture 116 is positioned on its outer surface. Stent 115 includesheavy stent cell density 117 and light stent cell density 118 along itsouter surface. As can be seen in FIG. 35, two stents 115 have beencombined so that the light density of one overlaps the light density ofthe other causing the combined stents to create relatively uniform heavycell density and thus providing relatively uniform heavy cell densityover the entire bifurcated vessel wall.

[0152] As shown in FIGS. 36A to 36C, two stents 115 are implanted tostent the bifurcation. For sake of clarity, as shown in FIG. 36A,apertured stent 115 shown implanted in the main vessel such thataperture 116 spans and provides an opening to the side-branch vesselwhile heavy stent cell density 117 provides full coverage of the distalmain vessel by stent 115. As depicted in FIG. 36B, apertured stent 115is partially implanted in the side-branch vessel and partially implantedin the main vessel, in this case with aperture 116 facing the continuinglumen of the main vessel. More specifically, heavy stent cell densityportion 117 is implanted in the side-branch vessel, while light stentcell density 118 is implanted in the main vessel, with aperture 116providing an opening for blood flow through the main vessel. It isintended that stent 115 be implanted first as seen in FIG. 36A and thata second stent 115 subsequently be implanted as shown in 36B or, byphysician preference, this sequence may be reversed. Thus, in FIG. 36C,both stents 115 have been implanted, and both apertures 116 provideopenings so that blood flow is unimpaired through both main vessel andside-branch vessel and no stent struts are left unopposed. The lightstent cell density portions 118 of both 115 stents overlap proximal tothe bifurcation, thereby insuring that there is full coverage of thebifurcated area by heavy stent cell density. Both stents 115 areimplanted with the catheter delivery system described herein whichincludes a positioning wire to accurately position and implant thestents in the bifurcated vessels.

[0153] While the invention herein has been illustrated and described interms of an apparatus and method for stenting bifurcated vessels, itwill be apparent to those skilled in the art that the stents anddelivery systems herein can be used in the coronary arteries, veins andother arteries throughout the patient's vascular system. Certaindimensions and materials of manufacture have been described herein, andcan be modified without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A stent delivery assembly for implanting aY-shaped stent in a bifurcated vessel having a side-branch vessel and amain vessel, comprising: a dual balloon Y-shaped catheter having aproximal end and a distal end, the catheter including a first expandablemember having a proximal end and a distal end, the catheter furtherincluding a second expandable member having a proximal end and a distalend; a first lumen for receiving a restraining member, the first lumenextending through at least a portion of the catheter including the firstexpandable member; a second lumen for receiving a guide wire, the secondlumen extending through at least a portion of the catheter including thesecond expandable member; and a restraining member positionable withinthe first lumen; wherein the first expandable member and the secondexpandable member are normally biased apart, but are restrained and heldtogether by the restraining member to provide a low profile duringdelivery of a Y-shaped stent.
 2. The stent delivery assembly of claim 1, wherein the restraining member is a mandril.
 3. The stent deliveryassembly of claim 1 , wherein the restraining member is a guide wire. 4.The stent delivery assembly of claim 1 , wherein the Y-shaped stent isremovably mounted on the first and second expandable members.
 5. Thestent delivery assembly of claim 1 , further including a removablelocking ring for assisting in holding the distal ends of the firstexpandable member and the second expandable member together prior toimplantation of the Y-shaped stent.
 6. The stent delivery assembly ofclaim 1 , wherein the first lumen includes a distal section, a portionof which extends through at least a portion of the second expandablemember.
 7. The stent delivery assembly of claim 6 , wherein therestraining member extends through the first lumen found on the firstexpandable member and the portion of the lumen on the second expandablemember to hold the first and second expandable members together untilthe assembly is to be deployed.
 8. A method of stenting a bifurcatedvessel having a bifurcation, a first vessel branch, and a second vesselbranch, comprising the steps of: providing a dual balloon Y-shapedcatheter having a proximal end and a distal end, the catheter includinga first expandable member having a proximal end and a distal end, thecatheter further including a second expandable member having a proximalend and a distal end; providing a first lumen for receiving arestraining member, the first lumen extending through at least a portionof the catheter including the first expandable member; providing asecond lumen for receiving a guide wire, the second lumen extendingthrough at least a portion of the catheter including the secondexpandable member; providing a Y-shaped stent mounted on the first andsecond expandable members; providing a restraining member andpositioning it within the first lumen such that the first expandablemember and the second expandable member are normally biased apart, butare restrained and held together by the restraining member; providing aguide wire and positioning the guide wire distally of the bifurcation inthe first vessel branch; loading the guide wire into the second lumen;advancing the catheter over the guide wire so that the catheter isadvanced proximate the bifurcation; withdrawing the restraining memberproximally until the first expandable member and the second expandablemember are released and spring apart; advancing a wire distally throughthe first lumen into the second vessel branch; advancing the catheterdistally over the wire and guide wire until the Y-shaped stent ispositioned at the bifurcation; implanting the Y-shaped stent byinflating the first and second expandable members; deflating the firstand second expandable members; and withdrawing the catheter, wire, andguide wire.
 9. The method of claim 8 , wherein the wire that is advancedthrough the first lumen into the second vessel branch is a guide wire.10. The method of claim 8 , wherein the wire that is advanced throughthe first lumen into the second distal branch is the restraining member.11. The method of claim 8 , further comprising the step of providing aremovable locking ring to assist in holding the first and secondexpandable members together prior to implantation of the Y-shaped stent.